leaflet version 2

#group by states 
library(dplyr)
data2 <- read.csv("nps2008.csv", header=T, na.strings=c("","NA"))
data3 <- data2[, c("R_STATE", "QB2_A","QB2_B","QB2_C","QB2_D")]
data3 <- na.omit(data3)

dplyr_data <- data3 %>% group_by(R_STATE) %>% summarise(Trust_Media = round(mean(QB2_B), digits = 2), Trust_Government = round(mean(QB2_A), digits =2), Trust_Police = round(mean(QB2_C),digits =2), Trust_LegalSystem = round(mean(QB2_D),digits =2), Overall_Trust = round((sum(mean(QB2_B) + mean(QB2_A) + mean(QB2_C)+ mean(QB2_D))/4),digits=2))

library(leaflet)
library(rgdal)

## Loading required package: sp

## rgdal: version: 1.2-5, (SVN revision 648)
##  Geospatial Data Abstraction Library extensions to R successfully loaded
##  Loaded GDAL runtime: GDAL 2.0.1, released 2015/09/15
##  Path to GDAL shared files: C:/Users/hanah/Documents/R/win-library/3.3/rgdal/gdal
##  Loaded PROJ.4 runtime: Rel. 4.9.2, 08 September 2015, [PJ_VERSION: 492]
##  Path to PROJ.4 shared files: C:/Users/hanah/Documents/R/win-library/3.3/rgdal/proj
##  Linking to sp version: 1.2-4

spdf <- tigris::states()

data_combine <- spdf@data%>% left_join(dplyr_data, by = c(STUSPS
 = "R_STATE"))

## Warning in left_join_impl(x, y, by$x, by$y, suffix$x, suffix$y): joining
## factor and character vector, coercing into character vector

spdf@data <- data_combine

m = leaflet(spdf) %>% 
    setView(lat=37.8, lng=-96 , zoom=4) %>%
    addTiles(group = "OpenStreetMap") %>%
    addProviderTiles(providers$Stamen.Toner, group = "Toner")  %>%
    addPolygons(group = "Trust Media",
      stroke = FALSE, fillOpacity = 0.5, smoothFactor = 0.5,
      color = ~colorNumeric("RdYlGn", Trust_Media)(Trust_Media),
      popup = paste("State:",spdf$STUSPS,"<br/>",
                    "Trust Media:",round(spdf$Trust_Media,2),"<br/>",
                    "Trust Government:",round(spdf$Trust_Government,2))) %>%
    addPolygons(group = "Tend to Trust Government", data = subset(spdf, Trust_Government>2.7),
                opacity = 1.0, stroke = TRUE, color = "black", fill = F,weight=2) %>%
    addLayersControl(
    baseGroups = c("Toner"),
    overlayGroups = c("Trust Media","Tend to Trust Government"),
    options = layersControlOptions(collapsed = TRUE))


  
m <- m %>% addLegend("bottomright", 
    pal = colorNumeric("RdYlGn", spdf$Trust_Media), values = ~Trust_Media,
    title = "Trust in Media", opacity = 0.5)

Hanah Chang - new map

leaflet version 2